A self-complexing gum blend is one that may be dissolved in an aqueous solution and then, after the gum portion is swollen, will complex or cross-link to form a water-resistant gel. Self-complexing blends are used in the explosive industry for making gelled explosive slurries. The blend is solvated in a saturated solution of ammonium nitrate and sodium nitrate in water. Once the blend is solvated, other ingredients, such an ammonium nitrate prills and aluminum metal, are usually added. At this point, the product is a viscous explosive slurry which is usually packaged in plastic bags. After packaging, the gum is cross-linked to form a water-resistant gel. The gel must form on standing overnight (about 16 hours). The gelled explosive slurry can then be used as an explosive in places where water is present.
It is known that antimony salts in which the antimony has a valence of plus three will cross-link guar gum at alkaline pH values. Alkaline pH values, however, desensitize aluminum metal. Therefore, this type of cross-linking is inappropriate for explosive slurries containing aluminum metal as a sensitizer.
It is also known that trivalent antimony salts, when oxidized with strong oxidizing agents, such as sodium dichromate, will immediately cross-link galactomannan solutions such as guar in acidic solutions, the cross-linking agent being antimony having a plus five valence. In this blend, however, a stiff water-resistant gel is formed in less than five minutes. The rate of cross-linking is too rapid for this blend to be used in the manufacture of packaged, gelled explosive slurries. Other examples of strong oxidizing agents which produce rapid cross-linking with antimony are calcium and sodium hypochlorites. A large number of oxidizing agents have been tested and most have not oxidized antimony from a valence of plus three to plus five or have done so so slowly as to be useless in the practical sense for manufacturing such items as packaged, gelled explosive slurries. Among such oxidizing agents are potassium perchlorate, sodium chlorate, potassium bromate, potassium persulfate, lead dioxide, manganese dioxide, stannic chloride, cobalt oxide, ceric ammonium sulfate and manganese oxalate.
Currently, self-complexing blends used in manufacturing explosive slurries are guar gum blended with 1 to 4% by weight potassium pyroantimonates based upon the weight of the gum portion. Pyroantimonates dissolve slowly in water releasing antimony with a valence of plus five. The pentivalent antimony cross-links the galactomannan gum. There are two disadvantages involved in using potassium pyroantimonates. The first is that not all commercially produced pyroantimonates will cause cross-linking of the galactomannan gum. The second is that those brands of potassium pyroantimonate which do produce cross-linking do so too rapidly, namely less than 1 hour, for efficient manufacturing procedures.